The present invention relates to a hydraulic power transmission joint which is used to distribute a driving force of a vehicle and, more particularly, to a hydraulic power transmission joint in which two power rotary shafts are coupled so as to be relatively rotatable and the torque corresponding to the rotational difference is transmitted.
Hitherto, a hydraulic power transmission joint is used to distribute the power to the front and rear wheels in a four-wheel drive vehicle or to distribute the power to the right and left drive wheels.
As such a hydraulic power transmission joint, for instance, there has been known a joint using a plunger pump mechanism as shown in U.S. Pat. No. 3,393,583 or 2,511,518.
However, in such conventional hydraulic power transmission joints, when a hydraulic pressure is generated by a stroke of a plunger in association with the relative rotation between a cam housing and a rotor, and the torque is transmitted, the heat generated is collected in the chamber in the rotor and the cooling efficiency is bad.
Therefore, even if the temperature of the oil suddenly rises upon transmission of the torque and the relative rotation is stopped and the torque transmission is stopped, the temperature of fluid does not so soon decrease. Thus, there are problems such that the oil deteriorates, quickly air suction occurs due to a volume phenomenon of the oil, and an abnormal abrasion of the cam and plunger occurs due to the deterioration in lubricating performance. On the other hand, there are also problems in that an oil leakage occurs due to the deterioration in the oil seal of each section, the normal operation cannot be executed, and the cam and plunger are burnt.
Further, since the plunger is reciprocated in the axial direction, there is a problem in that when a defective return or the like of the plunger occurs, an imbalance of the weight occurs, and vibrations result.
Moreover, since there is used a structure wherein the hydraulic chamber is shut in by assembling the plunger, there are problems in that no oil cannot be sealed into the hydraulic chamber after completion of the assembly, the assembling works must be executed while dipping the parts into the oil, the air bleed cannot be sufficiently executed, and the assembling costs are high.